Vestaxx window heating - experiences?

Every time I read this topic, my resting heart rate rises noticeably. For me personally, upon discovering this thread while researching a window heating system, the system would have been completely removed from the specifications list at the latest. I still have not seen a clear and transparently comprehensible calculation. What I have seen are long flowing texts with plenty of numbers that do not always match 100% from one text to another. The forum offers the possibility to upload screenshots. Here I would like to see clear data series presented side by side, where input parameters and results can be clearly read. I expect both from a studied managing director of a company with 25 years of professional experience in electrical engineering.

And then there are always these outliers in between. How are we supposed to argue reasonably? I am left only with the assumptions of missing expertise, or that facts are deliberately withheld or distorted for marketing reasons. Of course, you can determine the consumption of a house including all distribution losses with a heat meter. What else should one measure with it? Or put differently: The heat including all transmission losses remains in the house system and is thus sensibly utilized. They serve to warm the building structure. Gross = Net. Why should I care about what reaches the person?

I install a heat meter in the hydraulics: gross consumption
I install an electricity meter before the heat pump including the pump (with monoblock anyway a system): electricity consumption

Mixing both up = annual performance factor/COP or whatever.

imho still irrelevant, as gross/net consideration is already included via the heat meter.

So far, my question apparently got lost. how about manageable profitability calculations?

Basically, it bothers me that you argue here with "20-year-old" heat pump data from Fraunhofer and that a new builder should base their comparison solely on that. Otherwise, analogously, we would also have to refer to the 20-year-old insulation standard and compare there as well. The dogmatic attitude: annual performance factor 4-5? Impossible! No, it is possible! Source: me!

Since elsewhere the argument was again made with the transmission heat loss into the ground, which of course also occurs in your case. How do I sell the system to my wife and especially my mother-in-law then? Your floor then has (estimated) a maximum surface temperature of 20°C. So I can just subscribe to the "Snocks subscription" and keep slippers ready?

And then looking at it compared to the argument: What if you (Vestaxx) are no longer around in 20 years? Where will one get a replacement glass then?

That is a really important question because my personal opinion is that your customers will seriously care about this problem then.

Basically, it bothers me that here arguments are made using "20-year-old" heat pump data from Fraunhofer and with a dogmatic attitude: Annual performance factor 4-5? Impossible, source: me! Yes, it is possible and only with that should a new building owner make the comparison. Otherwise, by analogy, we would also have to refer to the 20-year-old insulation standard and compare there as well.

I have substantiated our example with an annual performance factor >4 heat pump from 2020 using actual numbers. In my opinion, that was answered in a waffle way and seasoned with the note "heat pump owners are all just being led by the nose," which can be interpreted with some imagination as "the poor idiots." When you then respond similarly confrontationally, it quickly becomes "too personal," but the answer again contained only waffle and no numbers. So let's wait until Monday, I guess, if RotorMotor's example is to be rebutted factually and with numbers. :)

Are the 25k already substantiated?

No, I simply took the number from V. to keep the discussions as short as possible.
So he had estimated 40k for the heat pump and 10k for Vestaxx, and I then added 5k for BWWP.

The difference even seems quite high to me, but I don't know exactly either.

Same here. But you can find prices for underfloor heating between 50 and 100€/m², so we would be at about 7500 to 15000€ here.
Then a heat pump for 15k€ including installation.
With a bit of small stuff, rather 30k€.

Against that, V. with 10k€ and BWWP remain rather 15k€ difference instead of 25k€.
But sure, all just estimates. I thought 17 years was already okay. So it’s more like 10 then.

The heating system may eventually wear out and need to be replaced, but the underfloor heating usually remains intact. That means the costs for the underfloor heating should basically be considered separately again.

Yes, for the heat pump I think you have to come under 20 years amortization, for the hydraulics probably 50?
But it doesn’t seem to be a problem at all. And the rising electricity prices only shift it towards a significantly faster amortization.

I’m eager to answer that immediately

Gladly, but please no long running texts, rather corrections/criticism on individual numbers.
And if you’re already making the effort, then with evidence instead of repeatedly claiming that a heat pump only has a seasonal performance factor of 3, although there are plenty of examples and studies showing 4 and 5 in new buildings! A study by the Fraunhofer Institute already gives 3.1 as an average for air-water heat pumps in old buildings, and they operate with a significantly higher flow temperature.

...
And then again and again the thing with the fear: What if we are no longer here in 20 years. There are 10 other manufacturers in Europe that produce heating glasses. I would be more worried about whether there will still be spare parts for my heat pump in 20 years and what they will cost.

...

I find that interesting. 10 other manufacturers of heating glasses? Is this more focused on other countries? If so, why? The German (quite large) market has so far probably not been relevant? Or are you rather small compared to other providers in Germany?

Vestaxx is thus (almost) alone in Germany - to my knowledge. Heated glass itself has existed for a long time, Interpane already offered such glass before 2010 and still has it in their program today. However, it is only offered for rooms with low heating demand or without conventional heating. The main application area (also for other specialist providers) is, to my knowledge, rather for conservatories, roof windows, and similar (e.g., to guarantee snow-free conditions or to prevent window fogging). There are also providers offering up to 300 degrees temperature - e.g., a sauna with a panoramic view at a mountain hotel at 2,500m altitude as a use case.

Otherwise yes, the heating works. It just spreads the classic acquisition costs of a heat pump over the runtime. And one simply has to calculate that. With 20 years of service life and - yes, that will come or has partially already been decided - mandatory photovoltaics, it can be an alternative. As a user, I would generally say: initially, keep your hands off until Vestaxx has become a mass supplier from a start-up (which also didn't work for Interpane). Photovoltaic rental models can also be worthwhile but are also nicely calculated there at first... It is no different here.

"Trust no statistic you haven't falsified yourself" - stay alert when buying heating systems

I have backed up our example with an annual performance factor >4 heat pump from 2020 based on actual figures. In my opinion, the response was answered in a convoluted way and seasoned with the note "heat pump owners are all just being led by the nose," which one could interpret with a bit of imagination as "the poor idiots."

That's exactly what I don't like, and that's why I also made a detailed remark to "Kill your darling." Here, someone is apparently rock-solid convinced of their product and clashes with anyone who questions it and raises concerns.

So, that annoys me so much here that I actually fired up Excel.



The result over typical financing periods, which at the same time represent the target lifespan of the heat pump, does not surprise me at all. I see all my theses and warnings about the system confirmed. If anyone asks me, I wouldn't recommend anyone the window heating system.

Since the topic of sustainability was also mentioned, I briefly checked that roughly as well. CO2e for German steel assumed to be about 2.5 kg, PE floor heating pipe 17x2 with 2 kg CO2e. Production overhead is calculated at a flat 25%.



By the way, I am also an engineer and occasionally deal with determining CO2 footprints at work, so I claim with my many years of expertise that these are good reference values.

Problematic, of course, is the CO2e of the German grid mix. Before the war, there were ambitious goals, which I now strongly doubt, especially since East German brown coal plants are still running. I simply assume that our government will achieve the <25% compared to 1990 target only ten years later in 2040.

So I simply calculated the electricity. Unfortunately, I have very serious doubts that it will run that well!


The very sobering result with the input parameters I chose is that over the 15-year lifespan, 16 tons of CO2 including production costs and operation are emitted more. The longer we continue this, the worse the CO2 balance of the window pane heating will become.



Significantly worse balance for the window heating compared to the heat pump, of course due to efficiency.

And now please do not argue with free photovoltaics. I have already disproved that argument with the first calculation. Over the financing period, there are no significant differences from a cost perspective, so photovoltaics should be considered on top in both cases. Furthermore, it should be noted that from November to February, 63% of the day not a single photon from the sun hits the photovoltaic surfaces directly. So 2/3 is heated with the grid mix and the last 1/3 is usually so overcast that even the 15 kWp south-facing photovoltaics cannot cover the base consumption of the house without heating. A few sunny days then make up for it again if there is no snow on the modules.

Photovoltaics and heating must be strictly separated for consideration. Therefore, in my opinion, it is extremely unfair that advertising with free photovoltaics is made here for the heating system.

Since I have not had enough yet, I will now take another look at my heating load calculation and raise a few more critical questions regarding heating the basement and my bathrooms, where I cannot install large window surfaces.